The invention relates to power converter circuits and switching power supplies.
The idea of “power supply on chip” or “system on chip” for high power conversion is a relatively recent idea. However, no single on-chip power converter has been reported in literature yet offering simultaneous high efficiency and adjustable conversion ratio. Integrated voltage regulators (IVR) are promising because they offer dynamically scalable power supplies in a cost effective manner. Switched capacitor IVRs can provide high efficiencies at reasonable current densities; however, achieving dynamic conversion ratio is very challenging with switched capacitor IVRs. Switched inductors converters (such as a buck converter) can provide high efficiency, high current density as well as offer continuous range of conversion. The bottleneck of this switched inductor IVR is the integration of power inductors on silicon.
In recent days, on chip inductors having spiral geometry and fabricated without magnetic materials exhibit inductances ranging from 1-10 nH. The densities of these inductors are lower than 100 nH/mm2; occupying a large substrate area. In order to fabricate a magnetic film that is compatible with standard CMOS processing technology is a challenging task. The magnetic material should have high temperature stability, a good deposition and etching technique, and compatibility with Si technology. Moreover, increasing inductance typically involves increasing the magnetic film thickness, which eventually results in increased eddy currents; therefore the peak quality factor is compromised. High quality factor inductors seem to have lower inductance density too. Therefore, significant research is still in place to design on-chip inductors with a high quality factor and small footprint.